DESCRIPTION: The applicants propose to extend the development of parallel functionality within their commercial quantum chemistry computer program, Q-Chem, for use on high-performance parallel computers (both shared and distributed memory) which can be used to carry out highly efficient quantum mechanical calculations on large molecular systems of biological interest. Q-Chem is particularly well suited for this project because: (1) it was written "from scratch" starting in 1993 and therefore takes full advantage of modern quantum chemistry methods such as the Continuous Fast Multipole Method for linear-cost Coulomb integral evaluation, and (2) it was designed from the beginning with parallelism in mind so many of the constructs necessary to achieve efficient scaling (both in terms of problem size and number of processors) are already built into the code. Indeed, they have recently carried out a DFT SCF calculation on a 352-atom conotoxin peptide at the S-VWN/3-21G level (1960 basis functions) in under 30 minutes on 32 processors of a Cray T3E. PROPOSED COMMERCIAL APPLICATION: NOT AVAILABLE